Neuromyelitis optica (NMO) is an inflammatory CNS syndrome distinct from multiple sclerosis
(MS) that is associated with serum aquaporin-4 immunoglobulin G antibodies (AQP4-IgG). Prior
NMO diagnostic criteria required optic nerve and spinal cord involvement but more restricted
or more extensive CNS involvement may occur. The International Panel for NMO Diagnosis (IPND)
was convened to develop revised diagnostic criteria using systematic literature reviews and electronic
surveys to facilitate consensus. The new nomenclature defines the unifying term NMO
spectrum disorders (NMOSD), which is stratified further by serologic testing (NMOSD with or
without AQP4-IgG). The core clinical characteristics required for patients with NMOSD with
AQP4-IgG include clinical syndromes or MRI findings related to optic nerve, spinal cord, area
postrema, other brainstem, diencephalic, or cerebral presentations. More stringent clinical criteria,
with additional neuroimaging findings, are required for diagnosis of NMOSD without AQP4-
IgG or when serologic testing is unavailable. The IPND also proposed validation strategies and
achieved consensus on pediatric NMOSD diagnosis and the concepts of monophasic NMOSD
and opticospinal MS. Neurology®2015;85:1–13